Alexander, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.3 °C (low) to 17.4 °C (high). Annual precipitation averages 1001.3 Millimeters. Alexander is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.2 °C | 1.8 °C | 53.85 mm |
| February | -5.3 °C | 4.6 °C | 48.51 mm |
| March | -0.2 °C | 11 °C | 71.12 mm |
| April | 5.6 °C | 18.1 °C | 104.9 mm |
| May | 12.1 °C | 23.6 °C | 120.65 mm |
| June | 17.2 °C | 28.3 °C | 120.14 mm |
| July | 18.9 °C | 29.9 °C | 99.82 mm |
| August | 17.7 °C | 29.2 °C | 85.85 mm |
| September | 13 °C | 26.4 °C | 86.11 mm |
| October | 6.7 °C | 19.5 °C | 78.49 mm |
| November | 0.7 °C | 11.2 °C | 76.2 mm |
| December | -4.2 °C | 4.7 °C | 55.63 mm |
| Annual | 6.3 °C | 17.4 °C | 1001.27 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |